XWIKI-21949: Restrict the execution of script macros during a realtime WYSIWYG editing session

* Fix a bug in EntityChannelScriptAuthorTracker which didn't lower / update the script level when the target entity reference had initially a low script level (e.g. when two users edit a page whose last author didn't have script right, one of them could use the rights of the other to execute scripts)
* Assume that a request can submit data associated with multiple documents (or document translations) so don't try to determine the entity that is targeted by the request; simply compute the effective author by taking the most recent author with the least script rights
* Update since versions

(cherry picked from commit fa1c0fb1)